The present invention relates to the catalytic production of the lower alcohols, methanol and mixtures of methanol with ethanol and propanol, by the reaction of carbon monoxide with liquid water or steam. The process is of particular advantage in that ethanol may be produced directly from carbon monoxide without resorting to a separate and additional process for the conversion of methanol to ethanol. Moreover, carbon monoxide can be provided as a by-product from the steel industry, from the partial oxidation of coal or other carbonaceous material, or from typical coal gasification processes without the necessity of water gas shift processing for increasing hydrogen content.
Previous processes for the production of methanol from carbon monoxide have involved the reaction of carbon monoxide with hydrogen. Copper, zinc and chromium oxides are often selected as catalysts for this process.
In contrast, the reaction of carbon monoxide and water to form methanol is thermodynamically more favorable than the corresponding carbon monoxide and hydrogen reaction. However, prior workers have been unable to realize this advantage at low process pressures by directly reacting carbon monoxide with water in the presence of these known catalysts. Consequently, the elevated process pressures with required thick-walled equipment negates many advantages of the carbon monoxide-water reaction.
The prior processes for the production of methanol from carbon monoxide have produced little ethanol. Subsequent process steps and operations are required for the further conversion of methanol to ethanol. Ethanol is a particularly desirable alcohol as it can be employed not only as a fuel but also as a raw material for the production of ethylene, a chemical used in large quantities in the industrialized countries. In addition, mixtures of methanol with ethanol and propanol are desirable as gasoline extenders. The presence of small amounts of ethanol and propanol prevent phase separation of methanol in the presence of water contamination.
Present processes for the production of methanol most often use raw materials from the steam reforming of methane in natural gases. Coal is not ordinarily used as a raw material as its high sulfur content may poison the catalyst. Also, the ordinary coal gasifier output must be further reacted with water to convert a portion of the carbon monoxide to additional hydrogen. Otherwise, the required two moles of hydrogen per mole of carbon monoxide are not available for methanol production. Catalysts for the water gas shift reaction are also poisoned by sulfur from coal.